Originally US 25 roughly followed what is now I-75 through Cincinnati, and north through Dayton, Lima, Toledo, and Detroit. From there it went to Port Huron MI via a road which today is signed with several different state and county highway numbers:

c. 1927, Rand McNally

This photo was taken on Military Street facing north towards Water Street (Lapeer Road):

Hargraves, 2005

This was probably where M-21 ended, which would have been a logical point to terminate US 25. In 1933, the US 25 designation was extended northward about 85 miles to Port Austin:

c. 1939, Rand McNally

This shot is facing west on Spring Street at the meeting point with Lake Street:

Hargraves, 2005

​US 25 most likely would have followed Port Au Barques Road into town, where it changed to Spring Street. Later on, US 25 was rerouted south, coming in on Grindstone Road to the south of Port Austin. That is the arrangement depicted on the 1970 USGS topo:

c. 1970, USGS

It is unclear from that map whether US 25 ended at its junction with M-53, or whether the designation was extended north to the center of town. But in the 1930s it was a fairly widespread practice to sign routes into the central business district. This picture was taken on Lake Street, looking north onto the intersection with Spring Street:

Hargraves, 2005

At first US 25 may have come in from the right on Spring, ending at the traffic signal. Later US 25 was rerouted to come in on Lake, ending there at Spring. The large image at the top of this page is from an old postcard, facing the same direction. The assembly visible at right indicated that US 25 and M-53 ended there, and M-25 began to the left.

US 25 was an original 1926 route; at the time it ran down to North Augusta SC, ending unceremoniously at the Georgia stateline for a few years. But Georgia picked up the route in 1929, extending the south end of US 25 to its junction with US 80 just west of Statesboro (USGS maps label this junction "Hopeulikit"). This shot was looking northwest along US 25-80:

Karners, Apr. 2014

​Today the highway curves to the right, and at the light in the distance, US 80 splits off by making a left turn. The road goes behind the trees in the center of the photo, and then re-emerges in the upper left corner. But in the '30s, US 80 followed the alignment visible along the left side of the photo, and right here is where the south beginning of US 25 split off to the right.

In 1938 the south end of US 25 was extended out of Statesboro along its current corridor, ending in Brunswick GA. It comes into Brunswick having been co-signed with US 341 for about 40 miles, from Jesup. At first, US 25 ended north of downtown (at Dock Junction, the same place where US 341 had ended since 1928), where those routes junctioned US 17 (more info on the Brunswick page).

After US 17 was rerouted to use the Sidney Lanier Bridge in 1956, US 25 and US 341 were extended into town along the former US 17. Traffic was originally directed through Brunswick on Newcastle Street, but today bypasses the downtown area via Bay Street. US 25 splits off onto Gloucester Street, and its last southbound trailblazer is just past Norwich Street:

Karners, Jan. 2017

Meanwhile, US 341 continues about a mile further south, then heads east on Fourth Avenue. Both routes end at their junctions with US 17, or Glynn Avenue. This photo was from eastbound Gloucester at Glynn:

Osbaldeston, Mar. 2002

There was some construction at that intersection in 2003, and some re-signing as well; here is how that same view looked in 2004:

Nitzman, July 2004

Nitzman, July 2004

Nitzman, July 2004

​US 25 is now co-signed with GA "Connector 25", while US 17 is overlapped with mainline GA 25... all of which served to make signage a bit more confusing. More recently, most of those signs have been removed, including (unfortunately) the "End" assembly:

Nitzman, Jan. 2014

The signage shown here is posted on northbound Glynn (US 17), at the south beginning of US 25:

Karners, Jan. 2017

The signs on the spanwire in the distance are shown close-up below...

Nitzman, July 2004

...and here is signage for traffic heading the opposite direction, on southbound Glynn:

Osbaldeston, Mar. 2002 (gone as of 2016)

Nitzman, July 2004

Turning to the west on Gloucester, the first northbound US 25 marker was posted at the intersection with Norwich. (Historically, US 25 traffic was directed to the right, and the east beginning of US 84 was straight ahead):

Karners, Jan. 2017

In 1974 the US 25 designation was eliminated in Michigan and Ohio. Since then, the north end of US 25 is in Covington KY (although there is a minor dispute about that). We will begin by heading west on KY hwy. 8 (4th Street) in Covington. Note that US 25 is still signed northbound from this point:

Moraseski/De Cesari, Nov. 2001 (still there as of 2013)

​That right turn puts drivers onto the Clay Wade Bailey Bridge over the Ohio River. More than halfway across the river, the bridge enters Ohio. At that point on the bridge used to be what was the last northbound US 25 sign:

Moraseski/De Cesari, Nov. 2001

Moses, Oct. 2013

All of those signs were replaced around 2008... except for the US 25 shield. H.B. noted that the specs of those signs suggest that they were installed by Ohio DoT, which does not consider US 25 to exist in their state. Neither does AASHTO, which lists Covington as the north endpoint of the route. The dispute arises because of a technicality: Kentucky maintains about 140 feet of the Ohio portion of the bridge. As a result, KYTC's internal description of US 25 has the designation extending to the end of the section they maintain (which is in Cincinnati city limits). However, this is most likely an error, because Kentucky does not have the authority to define a route outside of their borders. There is no question that they maintain the bridge a short distance into Ohio, but the bridge is designated US 25 only as far as the Ohio line.

Further evidence is visible in this photo, which was taken from westbound 3rd Street in Cincinnati. This is southbound US 42-127, both of which continue by turning left and crossing into Kentucky via the CWB Bridge:

Moraseski/De Cesari, Nov. 2001 (still there as of 2013)

Note the US 25 shield has a "JCT" above it: if US 25 existed in Ohio, there would be no need for that. But once drivers are on the bridge, it is not long before the first southbound US 25 sign is posted, right where the route officially begins:

Moraseski/De Cesari, Nov. 2001 (still there as of 2013)

That was heading south over the Ohio River, and (unlike its counterpart), a US 25 sign is still there (although it has been replaced since the photo above was taken).